Steel making processes



3,301,663 STEEL MAKING PROCESSES Adaibert Wicher, Dortmnnd-Reichsmark, and Rolf Pepe,

Dortmund-Lucklember, Germany, assignors to Dortmund-Hiirder Hiittenunion Aktiengesellschait, Bertmund, Germany No Drawing. Filed Apr. 23, 1964, Ser. No. 362,172 Claims priority, application Germany, Apr. 27, 1963, 1) 41,446; Nov. 26, 1963, 1) 43,024 3 Claims. (Cl. 75-58) The machining of steels by cutting has long been the subject of investigation. The cutting conditions, the type of tools, and the technological properties of the material it is required to machine have proved important influencing factors. The influence of steel inclusions on the steel cutting behaviour has also been examined. The findings of such research were initially contradictory be cause it was found that inclusions in the steel may have both an unfavourable and a favourable effect on cutting.

It was subsequently found that a welded layer forms on the tools in the case of steels having good cutting properties, and this welded layer prevents cratering and wear of the front rake of the tool. The formation of such a welded layer is due to non-metallic inclusions in the steel, such inclusions consisting of oxides or oxide compounds formed during deoxidation of the steel. It was not hitherto possible to find out accurately which oxides or oxide compounds have the greatest influence on the welded layers. In this connection it was proposed to improve the steel cutting properties by deoxidising the liquid melts with a calcium-silicon alloy.

It was then found that the uncertain behaviour of steels during cutting is particularly due to the fact that steels having homogeneous inclusions give a reduced tool wear only under specific conditions, particularly only over a narrow range of cutting speeds. Since the cutting speeds to be used during subsequent cutting are not known when the steels are manufactured, the known steps were unsuccessful.

The object of the invention is to improve the behaviour of steels which are to be cut at high cutting speeds, so that the steels give a long tool life over the entire range of practical cutting speeds.

To this end, according to the invention, the steel is deoxidised with a ferro-alloy which contains silicon, calcium, manganese and iron in the following proportions: 45-90% of silicon, 0.5-40% of calcium, 0.5-8% of manganese and remainder iron together with impurities. A deoxidation alloy containing up to 4% of aluminium as well is particularly advantageous.

To ensure that the welded layer forms on the tool irrespective of the temperatures at the tool tip during cutting and irrespective of the cutting speed, the following conditions must be observed:

(1) The inclusions forming on deoxidation must be uniformly distributed throughout the steel melt.

(2) The inclusions in the steel must have different melting points and (3) The residue analysis must be as indicated hereinafter.

The oxygen content of the steel melt plays an important part in the cutting of steels over different cutting speed ranges and varying temperatures. It should be 0.004 minimum and 0.1% maximum. These conditions can be readily obtained, for example by degasification ited States Patent Patented Jan. 31, 1967 ICC treatment of the steel. Also, the aluminium contained in the deoxidation alloy must not be such as to fix the quantity of free oxygen present in the steel. The proportion of aluminium in the deoxidation alloy must be such that the A1 0 content of the isolated residue after deoxidation is 45% maximum. The SiO content of the residue should be more than 50%, While the C210 content should be between 0.5 and 25%.

Good results for a welded layer have been obtained over a wide range of cutting speeds, namely from 60 to 400 metres per minute, with a steel whose oxygen content was between 0.005 and 0.006%. The deoxidation agent used was a ferro-alloy having an aluminium content of 1.2%. It may range from 1 to 1.5%. The silicon content of the ferro-alloy was about and its calcium content was approximately 7%. The residue analysis was as follows:

S20 65 percent. A1 0 21 percent. CaO 10 percent. Remainder Other oxides, for example manganese oxides.

The following residue analysis is desirable:

SiO 60-70 percent. A1 0 18-25 percent. CaO 8-12 percent. Remainder Other oxides, for example manganese oxides.

The melting point of the inclusions can be varied by variation of the aluminium and calcium content of the deoxidation alloy. This also influences the extent of the welded layer, because it depends on the composition and the melting points of the inclusions. The inclusions melt at higher temperatures for increasing aluminium oxide and calcium oxide contents. Higher cutting speeds then have to be used.

We claim:

1. A process for the manufacture of steels containing a fine distribution of nonmetallic inclusions and having good cutting properties over a wide range of cutting speeds, which comprises providing the steel with an oxygen content of 0.004 to 0.1%, deoxidizing the steel in the molten state with a ferro-alloy containing 45 to of silicon, 0.5 to 40% of calcium, up to 4% of aluminium, 0.5 to 8% of manganese and remainder iron in addition to impurities whereby a protective layer of oxidized inclusions will be formed on a tool cutting the steel.

2. A process according to claim 1 characterised in that the aluminium content of the deoxidation alloy is between 1 and 1.5%.

3. A process according to claim 1, wherein the aluminium content of theferro-alloy is such that it is not enough to fix all the oxygen in the steel.

References Cited by the Examiner UNITED STATES PATENTS 660,846 10/1900 Ehrensberger 75-58 3,000,731 9/1961 Ototani 75--58 3,137,570 6/1964 Michelson 75-58 3,215,525 11/1965 Sprankle 75-58 BENJAMIN HENKIN, Primary Examiner. 

1. A PROCESS FOR THE MANUFACTURE OF STEELS CONTAINING A FINE DISTRUBUTION OF NONMETALLIC INCLUSIONS AND HAVING GOOD CUTTING PROPERTIES OVER A WIDE RANGE OF CUTTING SPEEDS, WHICH COMPRISES PROVIDING THE STEEL WITH AN OXYGEN CONTENT OF 0.004 TO 0.1%, DEOXIDIZING THE STEEL IN THE MOLTEN STATE WITH A FERRO-ALLOY CONTAINING 45 TO 90% OF SILICON, 0.5 TO 40% OF CALCIUM, UP TO 4% OF ALUMINUM. 0.5 TO 8% OF MANGANESE AND REMAINDER IRON IN ADDITION TO IMPURITIES WHEREBY A PROTECTIVE LAYER OF OXIDIZED INCLUSIONS WILL BE FORMED ON A TOOL CUTTING THE STEEL 